Olefin polymerization catalysts are of great use in industry. Hence there is interest in finding new catalyst systems that increase the commercial usefulness of the catalyst and allow the production of polymers having improved properties.
Catalysts for olefin polymerization are often based on transition metal compounds, e.g., metallocenes, as catalyst precursors, which are activated either with the help of alumoxane, or with an activator containing a non-coordinating anion.
WO 2002/002576 discloses metallocene compositions and their use in the preparation of catalyst systems for olefin polymerization, particularly propylene polymerization. The bridged bis (2-R3-4-phenyl-indenyl) metallocenes described therein include those wherein at least one of the phenyl rings is substituted at the 3′ and 5′ positions by butyl groups which may be the same or different, e.g., tert-butyl.
US 2014/0057777, US 2014/0107301, and WO 2013/151863 disclose (Me2Si)2(Indenyl)2ZrCl2.
US 2003/0088038 discloses Me2Si—O—SiMe2 (indenyl)2ZrCl2.
Journal of Organometallic Chemistry, Vol. 585, 1999, pp. 18-25, discloses Si2Me4-bridged zirconocene dichlorides, such as meso-(Me2Si)2(Indenyl)2ZrCl2 and meso-Si2Me4(3-SiMe3-C9H5)2ZrCl2.
Other references of interest include: JP2011-137146A; WO 98/403331; and U.S. Pat. Nos. 7,405,261; 6,784,305; 6,376,408; 6,903,229; 8,058,461; 6,888,017; 6,376,413; 6,894,179; 6,380,123; 6,380,121; 6,380,334; 6,380,331; 6,376,410; 6,903,229; 6,376,408; 6,376,627; 6,376,412; 6,825,372; 6,380,124; 6,399,723; 6,380,120; 6,376,407; 6,414,095; 6,376,409; 6,376,411; 6,380,330; 6,936,675; 7,157,531; and U.S. Pat. No. 8,609,793.
There is still a need in the art for new and improved catalyst systems for the polymerization of olefins, in order to achieve specific polymer properties, such as high melting point, high molecular weights, to increase conversion or comonomer incorporation, or to alter comonomer distribution without deteriorating the resulting polymer's properties.